Tech companies could be taxed for their digital ad revenue, if a bill gets enough votes in Pennsylvania.

Over 300 advocates marched through the state capitol today in support of the tax policy. The group “Pennsylvanians for Accountability from Yass, Billionaires and Corporations” organized the rally. The group also regularly advocates for taxing capital gains of the wealthy and closing the “Delaware Loophole” for corporate taxes.

They estimate that $500 million in state revenue could come if digital ads were taxed.

In a press release, the group also called out lawmakers who receive campaign funds from big tech companies or investors.

An advocate from Erie said the tax could address structural deficits in the state budget.

“The governor is proposing that we use some of our rainy day funds to pay for operations. These bills, if they were to pass, would bring billions of dollars into our state,” said Martha Nwachukwu, the advocate from Erie. “There’s no reason why citizens are paying taxes, and those who are the most wealthy are not paying their fair share.”

A house bill on the topic could be brought for a committee vote this week.